Influence of compost amendment and maize root system on soil CO2 efflux: a mesocosm approach

Changes of the soil CO2 efflux in response to compost addition were investigated for 64 days by a mesocosm-style experiment located in a greenhouse. Each mesocosm was divided internally into four equal sectors and then filled with quartz sand or a soil/perlite mixture amended with increasing doses of orange waste compost (corresponding to 0, 18 and 36 t ha-1). Planted (with a maize plant grown in the central core space) and unplanted mesocosms allowed to separate basal respiration from the rhizosphere-derived CO2 efflux. Soil disturbance due to initial physical mixing promoted an extra release of soil organic matter-derived CO2 thus leading to an overestimation of the heterotrophic flux component: this "tillage effect" lasted for as long as 40 days. It was found that compost addition stimulated soil basal respiration. Whereas soil respiration increased with higher compost rates in soil-plant mesocosms due to the increasing contribution of the rhizosphere-derived CO2 efflux. The total CO2 efflux was statistically affected by soil temperature, but not by water content. Care is needed when using quartz sand as a reference substrate for calibrating closed dynamic chamber systems.